The Mammoth Hot Spring Terraces have
been a popular feature in Yellowstone since the early stagecoach routes
up the Yellowstone River Valley. The Terraces, first described by the
1871 Hayden Survey, were given the name of White Mountain Hot Spring,
even though they were well known and named before then.
The step-like terraces form as heated
water moves along the Morris-Mammoth Fault. The hot water carries dissolved
calcium and bicarbonate to the surface of the terraces where pressure
lessens. Carbon dioxide then escapes as gas and the carbonate combines
with calcium to precipitate as travertine.
The Mammoth Terraces are constantly changing
shape and color. Springs which were active one to five years ago may
be dry and lifeless now, yet activity may later resume. Along with changes
of thermal activity come changes in color. Fresh travertine is bright
white in color and as it weathers it changes to gray. Bright colored
cyanobacteria and algae mats which were dependent upon a stable temperature
and a flow of water also change as the microorganisms die creating a
stark, bleak landscape.
Height 45 feet. It received its name from the 1871 Hayden
Expedition for its resemblance
to the caps worn by colonial patriots in the Revolutionary War. The
cone formed from a steady flow
of hot water emerging from a single source, depositing dense layers
of travertine. The cone continued to grow as long as there was a source
of water. Either the hot water spring found a more convenient underground
channel to escape through or the orifice became sealed by travertine
deposits. It is now an inactive spring and it is not known when Liberty
Cap became extinct. The weathered outer surface now supports a plant
community of lichens, grass and even a small tree.
Temperature 160°F When this
feature received its name in 1871 by the Hayden Expedition, it was a
small spring with opal colors. it was dormant for several years until
1926 when it began to flow again. Since then it has intermittent activity.
During the 1940s Opal was very active and rapidly deposited porous travertine,
doubling its size. Nearly a foot of travertine deposited a year. The
terraces began encroaching on a tennis court and at first the deposits
were rerouted. By 1947 the tennis court was removed and the terrace
now covers the original site. Opal is still known for its pastel colors,
but like most Mammoth Terrace features it constantly changes activity,
shape and color.
MINERVA SPRING AND TERRACE
Temperature 161°F This spring
and terrace is considered one of the most colorful and ornate terraces
at Mammoth. Minerva has had periods of inactivity throughout its recorded
history, but when it is active terraces of porous travertine form rapidly.
During the building of a single terrace, orterracette, travertine precipitates
around the edge of a small pool, and can accumulate at a rate of as
much as 8.5 inches a year. As the water cascades from terrace to terrace
the water cools, allowing algae to grow. Blue-green algae and cyanobacteria,
in colors of green, yellow, orange and red, line the terrace run-off
ORANGE SPRING MOUND
Temperature 157°F Mound dimensions 48x20 feet. Orange cyanobacteria
which streak the large travertine mound are the origin of the name.
The spring from this mound is cooler than other thermal features at
Mammoth Terraces which allows orange-colored cyanobacteria to dominate.
The brilliant color changes from season to season depending on the flow
rate and the amount of available sunlight. The mound appears as a large
cone-shaped hot spring, but it actually formed along a fracture line
of a fissure ridge. Several cones have formed along this line of fracture,
including Tangerine Spring. Based on the low flow and deposition from
this spring and the size of the mound this formation may be very old.
NEW HIGHLAND SPRING
160°F The Highland Terrace area received its name from A.C. Peale, geologist
for the 1872 Hayden Expedition. There are many springs and pools in
the Highland Terrace area. Most have intermittent activity. New Highland
Spring began its activity during the early 1950s. Before that time it
was a grassy, wooded hillside. The Spring rapidly formed a massive deposit
of porous travertine. Trees on the hillside became engulfed by travertine
and now stand as skeletons. Like other thermal features at Mammoth Terraces,
New Highland Spring changes from season to season depending on water
flow and temperature.
CANARY SPRING AND TERRACE
Temperature 160°F This spring
is part of the Main Terrace, which includes Blue, Jupiter, Naiad and
Main springs. All the springs have had intermittent activity, but Canary
has been the most regular spring in the group. The name Canary was in
reference to the yellow filamentous algae growing along the edge of
the spring, and may have been named by the 1904 Hague Expedition. But
now Canary Spring is known for its ultramarine-colored pool. The water
flowing down the face of the terrace has created multi-colored bands
of algae and cyanobacteria.